Electrical bushing with cooling means

ABSTRACT

Electrical insulating oil-cooled bushing for transformers and the like. The inner tubular current-carrying conductor of the bushing is formed of a pair of concentric tubes forming an annular cooling duct therebetween with inlet and outlet apertures at opposite ends. Baffle tubes are arranged on opposite sides of the composite conductor to form two additional cooling fluid ducts so that cooling fluid introduced under pressure into the bushing is directed in three passes along the surfaces of the composite conductor. Cooling fluid leaving the interior of the bushing passes through apertured terminal blades for cooling the latter.

United States Patent 72] Inventors William A. Keen, Jr.

Cheshire; Joseph F. Lynch, Pittsiield, both 01 Mass. [21] Appl. No. 62,284 [22] Filed Aug. 10, 1970 [45] Patented Dec. 7, 1971 [73] Assignee General Electric Company [54] ELECTRICAL BUSHING WITH COOLING MEANS 10 Claims, 6 Drawing Figs.

[52] 0.8. CI. 174/15 811, 174/18 [51] Int. Cl "1310 1131754, 11011) 17/26 [50] Field of Search 174/11 8H, 12 B11, 1481-1, 15 81-1, 161311, 18, 31 R, 31 S [56] References Cited UNITED STATES PATENTS 1,706,810 3/1929 Paul 174/16Bl-1X 1,905,751 4/1933 Rankin 174/12 BH UX 2,130,888 9/1938 Marshall 174/15 BH 2,219,613 10/1940 Berghaus et a1. 174/15 BH 2,742,582 4/1956 Bahn et a1 174/15 BH X FOREIGN PATENTS 1,085,579 7/1960 Germany 174/31 R 443,017 2/1936 Great Britain 174/15 BH Primary Examiner-- Laramie E. Askin Attorneys-Sidney Greenberg, J. Wesley Haubner, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: 7 Electrical insulating oil-cooled bushing for transformers and the like. The inner tubular current-carrying conductor of the bushing is fonned of a pair of concentric tubes forming an annular cooling duct therebetween with inlet and outlet apertures at opposite ends. Bafile tubes are arranged on opposite sides of the composite conductor to form two additional cooling fluid ducts so that cooling fluid introduced under pressure into the bushing is directed in three passes along the surfaces of the composite conductor. Cooling fluid leaving the interior of the bushing passes through apertured terminal blades for cooling the latter.

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PATENTEUUEC 7|97| 3,626,079

SHEET 1- OF 4 il'lll l PATENTED DEC 7 |97| SHEET 3 BF 4 I i// 8a I 15 T PATENTEDDEB 71971 3.626.079

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ELECTRICAL BUSHING WITI-I COOLING MEANS The present invention relates to insulating bushings for electrical apparatus, and more particularly to such bushings of forced oil cooled type.

It is an object of the invention to provide an improved bushing of the above type, especially for carrying relatively high currents. I

It is another object of the invention to provide a bushing of the above type having improved cooling means so that the conducting parts of the bushing may be kept to minimum size without risk of excessive temperature rise during current flow.

Still another object of the invention is to provide a bushing of the above type having forced oil cooling means wherein improved cooling is provided for the current-carrying conductive parts thereof.

A further object of the invention is to provide a bushing of the above type wherein the cooling means include cooling fluid passages formed by readily assembled parts within the bushing.

Other objects and advantages will become apparent from the following description and the appended claims.

With the above objects in view, the present invention in one of its aspects relates to an electrical insulator bushing comprising, in combination, an outer electrically insulating housing having top and bottom openings, a tubular electrical conductor arranged concentrically within the insulating housing spaced from the inner surface thereof, the tubular conductor being open at top and bottom and formed with a first annular duct extending along the length thereof and having aperture means at opposite ends thereof opening respectively at opposite surfaces of the conductor, first closure means covering the top opening of the insulating housing and spaced above the tubular conductor, means fluidtightly sealing the insulating housing to the tubular conductor at their lower portions, second closure means covering the bottom opening of the tubular conductor, and inner tubular baffle open at its top and closed at its bottom arranged concentrically within and spaced from the inner surface of the tubular conductor and defining therewith a second annular duct, first fluid conduit means passing through the second closure means and the bottom of the inner tubular baffle and communicating with the interior thereof, and second fluid conduit means passing through the second closure means and communicating with the second annular duct, whereby cooling fluid introduced through one of the fluid conduit means may circulate through the first and the second annular ducts and the space between the insulating housing and the tubular conductor for cooling the surfaces of the latter.

The invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view in elevation, partly broken away, showing an oil-cooled electrical bushing embodying the invention in association with transformer apparatus;

FIG. 2 is a view, partly in section, of the bushing shown in FIG. 1;

FIG. 3 is a top plan view of the bushing;

FIG. 4 is a bottom plan view of the bushing;

FIG. 5 is an enlarged sectional view of the lower portion of the bushing; and

FIG. 6 is an enlarged sectional view of the upper portion of the bushing.

Referring now to the drawings, and particularly to FIG. 1, there is shown an oilinsulated transformer 1 comprising a tank 2 containing a transformer core and coil assembly 3 immersed in a dielectric liquid 4, such as mineral oil or chlorinated diphenyl. Mounted on the cover 5 of transformer tank 2 is an oil-cooled bushing 6, typically of high-current type, for conducting electrical current through tank cover 5 in electrically insulating relation thereto. Bushing 6 has an outer electrically insulating shell 7, such as porcelain, extending along its length with an upper external portion 7a formed of a series of discs disposed above tank cover 5 and a lower elongated portion 711 extending into the interior of oil-filled transformer tank 2 with its lower portion immersed in dielectric liquid 4. Attachment of bushing 6 to the tank cover is provided by clamping ring 14 which surrounds and is cemented to porcelain shell 7 and is secured to cover 5 by screws or the like. At its upper end, bushing 6 has a plurality of upstanding terminal blades forming part of upper terminal cap 8, and at its lower end has a pair of downwardly extending lower terminal blades 19 to which conducting leads (not shown) from the transformer core and coil assembly 3 may be connected. Also extending downwardly from the bottom end of bushing 6 is oil inlet tube 10 to which an oil supple conduit 11 is connected for flow of cooling oil into the bushing interior. A supply of oil for this purpose is provided by pump 12 which draws oil from transformer tank 2 and delivers it to chamber or header 13, from which the oil passes through conduit 11 to bushing inlet 10 under the force provided by operation of the pump.

FIG. 2 shows the interior construction of bushing 6 wherein a plurality of concentric ducts are provided to produce a laminar flow of cooling oil in multiple passes along the tubular conductor of the bushing. The bushing conductor comprises, in accordance with a feature of the invention, a composite tubular member 15 which is formed of concentrically arranged inner conducting cylinder 15a and outer conducting cylinder 15b joined together at top and bottom mating surfaces by brazing or other suitable means. CylinderslSa, 15b are typically made of copper, aluminum or other suitable electrically conductive material. The outer surface of inner cylinder 15a is recessed along most of its length between its opposite ends so as to define with the inner surface of cylinder 15b an annular duct 16 between the two cylinders for passage of cooling oil as shown. A plurality of circumferentially spaced apertures 17 in the lower portion of outer cylinder 15b and similar apertures 18 in the upper portion of inner cylinder 15a provide for entry and exit of the cooling oil passing through duct 16.

At its upper end, composite tubular conductor 15 is connected to terminal member 8 which is integrally formed with an annular cap 8a surrounding and secured (e.g., by brazing) to tubular conductor 15, a top terminal plate portion 8b extending across the open end of tubular conductor 15, and upstanding terminal blades 8c. Terminal cap 8a is formed with a plurality of circumferentially spaced apertures 8d. At its lower end composite tubular conductor 15 is joined to a bottom terminal plate 20 having terminal blades 19 integral therewith. Porcelain shell 7 surrounds tubular conductor 15 in radially spaced relation thereto. Conductor 15 is secured at its threaded bottom portion by means of bottom nut 21 to the bottom end of porcelain shell 7, with a spring assembly 22 and washer-gasket assembly 23 arranged therebetween as seen in FIG. 2. By this means, the bottom of porcelain shell 7 is fluidtightly sealed to tubular conductor 15 and is resiliently urged upwardly so that its upper end is pressed against top terminal plate 8b with an intervening gasket to provide a fluidtight seal at that end.

At the upper end of tubular conductor 15, as seen best in FIG. 6, is an annular main sealing ring 25 having a plurality of circumferentially spaced holes each formed to receive the lower portion of a spacer member 26 which is in sealing engagement with sealing ring 25 below it, and also in sealing engagement with a venting ring 27 received in an annular recess in the bottom surface of terminal plate 8b. Spacer member 26 has a passage 26a extending therethrough which communicates at its bottom with the interior of conductor 15 through the hole in sealing ring 25, and at its top with annular channel 270 formed in and extending around the top surface of venting ring 27. A plurality of vent plugs 28 are inserted in circumferentially spaced openings in terminal plate 8b communicating with venting channel 27a, so that when vent plugs 28 are removed, air may be expelled from the oil ducts in the interior bushing structure when oil is introduced therein during installation. Another vent plug 29 (see FIG. 3) is arranged in a central opening of terminal plate 8b to permit similar venting of the interior space beneath that part.

An outer cylindrical baffle 30 is arranged surrounding tubular conductor 15 in concentric spaced relation thereto so as to define therewith an outer annular duct 31 open at its top which confines the flow of oil in an annular laminar passage along the outer surface of tubular conductor 15b. The bottom of baffle tube 30 is fluidtightly sealed to washer assembly 23, (e.g., by welding) so as to close the bottom opening and hold bafi'le tube 30 in position.

An inner baffle tube 35 is arranged within composite tubular conductor 15 in concentric spaced relation thereto to define therewith an inner duct 36 which confines the flow of oil in an annular laminar passage along the inner surface of tubular conductor 15a. Inner baffle tube 35 is closed at its bottorn by seal plate 37 which is fluidtightly sealed at its periphery to the bottom edge of baffle tube 35 (e.g., by welding). The bottom opening of conductor tube 15 is closed by terminal plate 20. At its top, baffle tube 35 has joined thereto a complementary sealing ring 40 which has a sloped annular outer surface mating with a corresponding beveled surface at the inner corner of main sealing ring 25. Complementary sealing ring 40 is urged into mating engagement with main sealing ring 25 by virtue of a spring-loaded support assembly 41 (see FIG. at the bottom of seal plate 37. Support assembly 41 comprises a housing 42 formed with a plurality of spaced recesses 43 opening at the bottom of housing 42 and containing compressible coil springs 44. A separable washer 45 at the bottom of housing 42 covering recesses 43 is held in closed position against housing 42 and holds springs 44 in compressed condition by means of clamping nut 46 threaded in bottom terminal plate 20. Clamping nut 46 is formed with holes 47 passing therethrough by which it may be turned with a spanner wrench for adjustment toward and away from spring housing 42. Holes 47 serve additionally as outlets for outward passage of cooling oil from the interior of bushing 6. By virtue of the described arrangement, inner baffle tube 35 is resiliently held in assembly within the bushing with its upper complementary sealing ring 40 constantly urged into operative sealing engagement with main sealing ring 25. The mutually engaging sloped surfaces of the mating sealing rings 25, 40 retain the upper end of baffle tube 35 in properly centered position.

Centering pin 50 threaded into spring housing 42 and extending downwardly into a complementary recess 51 in clamping nut 46 aids in retaining spring housing 42 in proper position.

Oil inlet tube extends upwardly through bottom terminal plate with a slight clearance therein and through bottom seal plate 37 in threaded engagement therewith, serving thereby to introduce cooling oil into the interior of the bushing and also to aid in retaining the lower end of bafile tube 35 in properly centered position. Locater pin 52 likewise threaded into bottom seal plate 37 and passing with slight clearance through bottom terminal plate 20 also contributes to proper centering of baffle tube 35.

Terminal blades 19 are flat, electrically conductive members integral with and projecting downwardly from terminal plate 20. Each terminal blade 19 is formed with a plurality of spaced holes 190 (see FIGS. 2 and 4) extending therethrough from top to bottom and in register with corresponding holes in terminal plate 20, so that cooling oil is enabled to flow from within the bushing outwardly through holes 19a, thereby cooling terminal blades 19.

In the operation of the bushing cooling structure thus described, oil or other cooling fluid is introduced under pressure through inlet 10 into the interior of inlet baffle tube 35 and flows upwardly to the top of the latter, from where it passes outwardly through the space between the top of sealing rings and 40 and the bottom of terminal plate 8b, then through the plurality of apertures 8d in terminal cap 80, downwardly through outer duct 31 and into duct 16 through apertures 17, upwardly through duct 16 and out through apertures l8, and then down through duct 36. The cooling fluid then passes downwardly and out of the bushing into transformer tank 2 through terminal blade holes 19a and clamping nut holes 47 as previously mentioned, as well as through a number of supplementary outlet holes 200 in bottom terminal plate 20 (see FIG. 4).

The oil in transformer tank 2 is cooled in conventional manner by dissipation of heat from the tank walls or by use of finned tubes thereon (not shown), or other suitable means.

By virtue of the described structure, there is provided an insulating bushing having three concentric cooling ducts connected in series with each other and extending substantially the entire length of the tubular conductor therein for effectively cooling the four surfaces of the composite conductor 15. in conjunction therewith, passages provided in the lower terminal blades l9 of the bushing for outward flow of the cooling fluid serve to cool the terminal blades at the same time. The described supporting arrangement for the inner baffle tube 35 enables the latter to be readily mounted in the bushing while assuring its proper position to provide the desired passages for flow of the cooling medium.

While the cooling medium is typically composed of an oil dielectric liquid as mentioned above, it will be understood that other cooling liquids or fluids could be used, such as air or other gases. it will also be understood that the invention is applicable to bushing and like devices which may be used in conjunction with types of electrical apparatus other than transformers, such as circuit breakers, generators and other currentcarrying devices of various kinds.

The improved cooling results produced by the bushing structure of the invention makes it possible to increase the current rating of the bushing without employing larger conductors therefore which would make necessary a larger overall bushing size. The invention also avoids the need for a plurality of parallel bushings such as previously used where very high currents are involved, and as a result substantial advantages are obtained in dispensing with the additional tank holes, bus and cable connections, along with the attendant expense, which should otherwise be required.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the scope of the invention. Therefore, the appended claims are intended to cover all such equivalent variations as come within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical insulator bushing comprising, in combination, an outer electrically insulating housing having top and bottom openings, a tubular electrical conductor arranged concentrically within said insulating housing spaced from the inner surface thereof, said .tubular conductor being open at top and bottom and formed with a first annular duct extending along the length thereof and having aperture means at opposite ends thereof opening respectively at opposite surfaces of said conductor, first closure means covering the top opening of said insulating housing and spaced above said tubular conductor, means fluidtightly sealing said insulating housing to said tubular conductor at their lower portions, second closure means covering the bottom opening of said tubular conductor, an inner tubular baffle open at its top and closed at its bottom arranged concentrically within and spaced from the inner surface of said tubular conductor and defining therewith a second annular duct, first fluid conduit means passing through said second closure means and the bottom of said inner tubular baffle and communicating with the interior thereof, and second fluid conduit means passing through said second closure means and communicating with said second annular duct, whereby cooling fluid introduced through one of said fluid conduit means may circulate through said first and said second annular ducts and the space between said insulating housing and said tubular conductor for cooling the surfaces of the latter.

2. A device as defined in claim 1, main annular seal means at the top of said tubular conductor concentric therewith, and complementary annular seal means at the top of said inner tuannular duct.

3. A device as defined in claim 2, and vent means in said first closure means for venting the ducts formed by said tubular conductor and said tubular baffle.

4. A device as defined in claim 2, and support means arranged between said second closure means and the bottom of said inner tubular baffle for holding said complementary annular seal means in mating engagement with said main annular seal means.

5. A device as defined in claim 4, said support means comprising resilient means urging said inner tubular bafi'le upwardly.

6. A device as defined in claim 5, including means for locating said inner tubular baffle in substantially concentric relation to said tubular conductor.

7. A device as defined in claim 1, said first and second closure means comprising conductive bushing terminal means.

8. A device as defined in claim 1, said second closure means comprising electrically conductive terminal means, said second conduit means comprising second aperture means extending through said terminal means, whereby the latter is adapted to be cooled by cooling fluid passing therethrough.

9. A device as defined in claim 1, an outer tubular baffie arranged in the space between said insulating bushing and said tubular conductor and defining with the latter a third annular duct.

10. A device as defined in claim 1, an electrical apparatus comprising container means, dielectric fluid in said container means, said bushing means being mounted on said container means with its lower portion extending into the interior thereof, and means for introducing dielectric fluid from said container means under pressure into said bushing through said one fluid conduit means for forced circulation through said ducts. 

1. An electrical insulator bushing comprising, in combination, an outer electrically insulating housing having top and bottom openings, a tubular electrical conductor arranged concentrically within said insulating housing spaced from the inner surface thereof, said tubular conductor being open at top and bottom and formed with a first annular duct extending along the length thereof and having aperture means at opposite ends thereof opening respectively at opposite surfaces of said conductor, first closure means covering the top opening of said insulating housing and spaced above said tubular conductor, means fluidtightly sealing said insulating housing to said tubular conductor at their lower portions, second closure means covering the bottom opening of said tubular conductor, an inner tubular baffle open at its top and closed at its bottom arranged concentrically within and spaced from the inner surface of said tubular conductor and defining therewith a second annular duct, first fluid conduit means passing through said second closure means and the bottom of said inner tubular baffle and communicating with the interior thereof, and second fluid conduit means passing through said second closure means and communicating with said second annular duct, whereby cooling fluid introduced through one of said fluid conduit means may circulate through said first and said second annular ducts and the space between said insulating housing and said tubular conductor for cooling the surfaces of the latter.
 2. A device as defined in claim 1, main annular seal means at the top of said tubular conductor concentric therewith, and complementary annular seal means at the top of said inner tubular baffle engaging said main annular seal means in sealing relation therewith and closing the upper end of said second annular duct.
 3. A device as defined in claim 2, and vent means in said first closure means for venting the ducts formed by said tubular conductor and said tubular baffle.
 4. A device as defined in claim 2, and support means arranged between said second closure means and the bottom of said inner tubular baffle for holding said complementary annular seal means in mating engagement with said main annular seal means.
 5. A device as defined in claim 4, said support means comprising resilient means urging said inner tubular baffle upwardly.
 6. A device as defined in claim 5, including means for locating said inner tubular baffle in substantially concentric relation to said tubular conductor.
 7. A device as defined in claim 1, said first and second closure means comprising conductive bushing terminal means.
 8. A device as defined in claim 1, said second closure means comprising electrically conductive terminal means, said second conduit means comprising second aperture means extending through said terminal means, whereby the latter is adapted to be cooled by cooling fluid passing therethrough.
 9. A device as defined in claim 1, an outer tubular baffle arranged in the space between said insulating bushing and said tubular conductor and defining with the latter a third annular duct.
 10. A device as defined in claim 1, an electrical apparatus comprising container means, dielectric fluid in said container means, said bushing means being mounted on said cOntainer means with its lower portion extending into the interior thereof, and means for introducing dielectric fluid from said container means under pressure into said bushing through said one fluid conduit means for forced circulation through said ducts. 